Axillary lymph nodes

Editorial Board Member: Emily S. Reisenbichler, M.D.
Mary Ann Gimenez Sanders, M.D, Ph.D.

Topic Completed: 1 January 2018

Minor changes: 14 May 2021

Copyright: 2002-2021,, Inc.

PubMed Search: Axillary lymph node[TI] examination[TIAB] breast[TI]

See also: Sentinel nodes

Mary Ann Gimenez Sanders, M.D, Ph.D.
Page views in 2020: 3,435
Page views in 2021 to date: 2,987
Cite this page: Sanders MAG. Axillary lymph nodes. website. Accessed October 25th, 2021.
  • Macrometastases: > 2.0 mm
  • Micrometastases: ≤ 2.0 mm or > 200 cells in a single histologic cross section
  • Isolated tumor cells (ITCs): ≤ 0.2 mm or < 200 cells in a single histologic cross section
Clinical features
  • Presence of axillary lymph node metastases is the most important prognostic factor for disease free and overall survival in the absence of distant metastasis and is important for determining treatment
  • Patients with early stage breast cancer:
    • If no sentinel lymph node (SLN) metastasis, then no axillary lymph node dissection (ALND)
    • If 1 or 2 SLNs with metastases and undergoing breast conserving surgery with whole breast radiotherapy, then no ALND
    • If SLN metastases and undergoing mastectomy, then ALND should be offered (J Clin Oncol 2017;35:561)
  • ALND can be avoided in patients with early stage breast cancer and only micrometastasis in the SLNs (Lancet Oncol 2013;14:297)
  • Intraoperative evaluation of sentinel lymph nodes can be avoided in most patients who are clinically node negative and undergoing breast conserving surgery (Arch Pathol Lab Med 2016;140:830)
  • Additional evaluation of SLNs to detect occult metastasis, including multiple levels and cytokeratin immunohistochemistry, offers no clinical benefit (N Engl J Med 2011;364:412)
  • Lymph node dissection of level I and level II of the axilla should contain 10 or more lymph nodes
  • Regional lymph nodes:
    • Axillary (ipsilateral), subdivided as follows:
      • Level I (low axilla): lateral to the lateral border of pectoralis minor muscle
      • Level II (mid axilla): between medial and lateral borders of pectoralis minor muscle, plus the interpectoral (Rotter) lymph nodes
      • Level III (apical axilla): medial to the medial margin of the pectoralis minor muscle, including those designated as apical, excluding those designated as subclavicular or infraclavicular
    • Infraclavicular (subclavicular, ipsilateral)
    • Internal mammary (ipsilateral): lymph nodes in the intercostal spaces along the edge of the sternum in the endothoracic fascia
    • Supraclavicular (ipsilateral)
  • Side effects of axillary nodal dissection include lymphedema, shoulder restriction, numbness, weakness and pain syndromes (Cancer J 2008;14:216)
  • Lymph nodes are thinly sliced at 2 mm intervals (to detect all macrometastasis)
    • All lymph node tissue is submitted for histologic evaluation
    • If grossly positive then a representative section, including any possible areas of extranodal extension, is adequate
  • Size of a metastatic deposit consists of a contiguous focus of tumor cells, including any intervening desmoplasia (for postneoadjuvant treatment, do NOT include intervening fibrous tumor bed for deposit size)
  • Tumor cells of metastatic lobular carcinoma are often dispersed and not contiguous
    • 200 cell cutoff helps to determine if dispersed cells in a lymph node should be classified as isolated tumor cells
  • Extranodal extension is included in the size of the metastatic deposit
    • Extension into the fatty hilum of a lymph node is not considered extranodal extension
  • Tumor deposits are counted as axillary lymph nodes completely replaced by tumor
  • Presence of treatment effect (fibrosis with or without macrophages or hemosiderin) after neoadjuvant chemotherapy is an important prognostic factor
  • pN stage:
    • pN0(i+): isolated tumor cells
    • pN1mi: micrometastases
    • pN1a: metastases in 1 - 3 axillary nodes, at least 1 macrometastasis
    • pN2a: metastases in 4 - 9 axillary nodes, at least 1 macrometastasis
    • pN3a: metastases in 10 or more nodes, at least 1 macrometastasis
  • (sn) modifier for pN stage is used when 5 or less lymph nodes are sampled / evaluated
  • Intramammary lymph nodes are included in the axillary lymph node count
  • Metastasis to a contralateral axillary lymph node is staged as pM1
Radiology images

Contributed by Dr. Mark R. Wick
Case reports
Microscopic (histologic) images

Scroll to see all images:

Contributed by Dr. Mary Ann Gimenez Sanders

Core biopsy: negative

Müllerian type inclusion

Müllerian type inclusion, PAX8+

Treatment effect: fibrosis

Treatment effect: pancytokeratin+ tumor

False positives (i.e. not metastatic breast carcinoma):

Intramammary lymph node

Lactational histiocytosis

Heterotopic glands with structure of mammary lobule

Myoepithelial cells
(arrows) and
basement membrane
are present

Clusters of nevus cells have indistinct cell borders and small uniform nuclei and are S100+ (as are histiocytes)


Tattoo pigment

Dilated dermal
vascular channels
with prominent
endothelial cells

Hyperkeratosis, thickened
dermis with edema, elastosis,
fibrosis, congested capillaries
(arrow) and lymphocytes

hyperkeratosis, dilated
dermal vascular channels

Metastatic ovarian serous papillary adenocarcinoma

Contributed by Dr. Mark R. Wick

Various images

Images hosted on other servers:

Metastatic breast carcinoma and melanoma

Cytology images

Images hosted on other servers:

Various images


Histopathology lymph node - metastatic breast carcinoma

Differential diagnosis
Board review style question #1
Recommendations provided by the College of American Pathologists for evaluating axillary lymph nodes in breast cancer include which of the following:

  1. Evaluate 3 H&E levels for sentinel lymph nodes.
  2. Submit all lymph node tissue if grossly positive.
  3. Thinly slice each lymph node at 2 mm intervals.
  4. Tumor deposits in axillary tissue are counted as extranodal extension.
  5. Use cytokeratin immunohistochemistry on all negative lymph nodes.
Board review style answer #1
C. Thinly slice each lymph node at 2 mm intervals. Per the CAP guidelines, sampling of lymph nodes must be adequate to detect all macrometastasis (> 2 mm deposit). Therefore, all lymph nodes must be thinly sliced at 2 mm intervals. All tissue from grossly negative lymph nodes must be submitted for histologic evaluation. For grossly positive lymph nodes, a representative section including areas suspicious for extranodal extension is adequate. Additional evaluation, including multiple H&E levels and cytokeratin immunohistochemistry, increases detection of isolated tumor cells and micrometastasis (occult metastasis), however this provides minimal clinical benefit. Therefore, the CAP recommends evaluating 1 H&E level from the surface of the tissue block when lymph node tissue has been sliced at 2 mm intervals. Tumor deposits in axillary tissue are counted as positive axillary lymph nodes (lymph node replaced by tumor).

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